Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuine behavioral detail beyond that: prefecture filtering excludes nationwide systems (requiring prefecture="全国"), and purposes collapses certain categories. It omits behavior of accepting_only (default true) and limit, which are meaningful filtering defaults.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the core purpose and the preferred alternative before detailing parameter quirks. Dense but each sentence adds operational value; no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present, return values need not be described, and the key scoping quirks are covered. The main gap is unstated behavior for accepting_only (default true) and limit, which can affect result sets.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% across 5 parameters, so the description carries the burden. It explains prefecture and purposes semantics well and implies keyword is a single term, but limit and accepting_only are left entirely undocumented in both schema and description.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (raw keyword search) and resource (J-Grants subsidies), and explicitly distinguishes itself from recommend_subsidies by noting it does not judge by company conditions. An agent can tell what it does and how it differs from the sibling without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly names the preferred alternative ('通常は recommend_subsidies を使う') and the condition that separates them (raw keyword search vs. company-condition judgement). Clear routing context, though it never states an explicit when-not/exclusion beyond the alternative pointer.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.